The invention relates to improvements in a plasma processing chamber and to a method of processing a substrate in the plasma processing chamber such as by plasma etching an oxide layer on a semiconductor wafer.
Vacuum processing chambers are generally used for chemical vapor depositing (CVD) and etching of materials on substrates by supplying process gas to the vacuum chamber and application of an RF field to the gas. Examples of parallel plate, transformer coupled plasma (TCP(trademark), also called ICP), and electron-cyclotron resonance (ECR) reactors are disclosed in commonly owned U.S. Pat. Nos. 4,340,462; 4,948,458; and 5,200,232. The substrates are held in place within the vacuum chamber during processing by substrate holders.
Conventional substrate holders include mechanical clamps and electrostatic clamps (ESC). Examples of mechanical clamps and ESC substrate holders are provided in commonly owned U.S. Pat. No. 5,262,029 and commonly owned U.S. Pat. No. 5,671,116. Substrate holders in the form of an electrode can supply radiofrequency (RF) power into the chamber, as disclosed in U.S. Pat. No. 4,579,618. According to U.S. Pat. No. 5,292,399, metal surfaces of wafer support and clamping ring mechanisms can be covered with insulating material to prevent erosion by the plasma and electrically conductive material can be used to reduce arcing due to charge build-up on such insulation surfaces.
Plasma processing systems wherein an antenna coupled to a radiofrequency (RF) source energizes gas into a plasma state within a process chamber are disclosed in U.S. Pat. Nos. 4,948,458; 5,198,718; 5,241,245; 5,304,279; and 5,401,350. In such systems, the antenna is located outside the process chamber and the RF energy is supplied into the chamber through a dielectric window. Such processing systems can be used for a variety of semiconductor processing applications such as etching, deposition, resist stripping, etc.
An object of the present invention is to reduce metal and/or particle contamination of plasma processed substrates when substrates are processed continuously by using silicon carbide as the material of one or more reactor surfaces such as a chamber liner surrounding the substrate holder, a focus ring surrounding the substrate, a baffle plate between the liner and substrate holder, and/or a gas distribution plate facing the substrate.
According to one aspect of the invention, a method of processing a substrate and reducing contamination thereof comprises placing a substrate on a substrate holder in a processing chamber wherein a member such as a liner, gas distribution plate, baffle plate and/or focus ring forms an exposed surface in the processing chamber in an area adjacent the substrate holder, the member comprising a silicon carbide based material and the member being effective to minimize particle and/or metal contamination of the substrates during the processing step as a result of reduced plasma potential on the silicon carbide member and/or reduced sputtering of non-silicon carbide chamber interior surfaces. The method includes processing the substrate by supplying process gas to the processing chamber and energizing the process gas into a plasma state such as by inductively coupling RF energy through the gas distribution plate into the processing chamber and consecutively processing substrates in the processing chamber by contacting the substrates with the plasma gas. The processing chamber can include a substantially planar antenna and the process gas can be energized into the plasma state by supplying RF power to the antenna. The plasma can comprise a high density plasma and the substrates can be processed by etching an oxide layer on the substrates with the high density plasma while supplying an RF bias to the substrates. The member preferably consists essentially of hot pressed, sintered, CVD or reaction bonded SiC.
According to another aspect of the invention, a plasma processing chamber includes a member comprising a silicon carbide based material, the member comprising a chamber liner, a focus ring, a baffle plate and/or a gas distribution plate. The chamber further includes a substrate holder for supporting a substrate within the processing chamber, a gas supply supplying process gas to an interior of the chamber, and an energy source such as an RF energy source which supplies RF energy into the chamber to energize the process gas into a plasma state. The chamber can further include a dielectric window adjacent the gas distribution plate and the RF energy source can comprise a substantially planar antenna adjacent the window, the antenna supplying RF power through the window to energize process gas in the processing chamber into a plasma state. The antenna can be arranged such that the gas outlets in the gas distribution plate are not directly between the substrate holder and the antenna. The dielectric window can have a substantially uniform thickness and substantially planar configuration and the gas distribution plate can have a substantially uniform thickness and substantially planar configuration.